Spatial and temporal dynamics of the male effective population size in bumblebees (Hymenoptera: Apidae)

Abstract

Eusociality and male haploidy of bumblebees (Bombus spp.) enhance the deleterious effects of population decline and aggravate the degeneration of population fitness compared to solitary and diploid species. The highly dispersive male sex may be the prime driver to connect otherwise isolated populations. We therefore studied the temporal and spatial structure of the male population of Bombus terrestris (Linnaeus 1758) and Bombus lapidarius (Linnaeus 1758) using microsatellite DNA markers. We found that the majority of the males in a 1000 m 2 sampling area originated from colonies located outside of the workers foraging range, which was consistent with the genetic distances among colonies. The analyses of temporal population sub-structure based on both colony detection rate over time and the clustering software STRUCTURE consistently suggested one large and temporally unstructured male population. Our results indicate an extended male flight distance for both species. Though the range of queen dispersal remains to be studied, the effective size (N e ) of bumblebees is increased by extended male mating flight ranges (A m ) exceeding worker foraging distance by factor 1.66 (A m = 69.75 km 2 ) and 1.74 (A m = 13.41 km 2 ), B. terrestris and B. lapidarius, respectively. Thus this behaviour may counteract genetic deprivation and its effects. All populations were genetically highly diverse and showed no signs of inbreeding. We discuss the implications of our findings in context of bumblebee population dynamics and conservation. We also highlight the effects and benefits of sampling both workers and males for population genetic studies.

Contemporary human‐altered landscapes and oceanic barriers reduce bumble bee gene flow

“…), it is possible that males may be especially capable of long‐distance dispersal, although few studies have attempted to quantify male bumble bee dispersal ( but see Wolf et al . ).…”

Sex differences in pollinator behavior: Patterns across species and consequences for the mutualism

“…As such, males are often observed to be more mobile than females. Bombus terrestris males' minimum dispersal distance from their natal colony has been estimated to be larger than the maximum female foraging range (Kraus, Wolf, & Moritz, 2009;Wolf et al, 2012). High mobility in males has been observed in a number of pollinating species, such as Lysandra bellargus butterflies, in which males fly longer distances than females between successive flowers (Rusterholz & Erhardt, 2000), and in hunchback flies (Acroceridae), in which males visit fewer flowers per patch and move more quickly to new patches compared to females (Borkent & Schlinger, 2008).…”

Effective population size as a driver for divergence of an antimicrobial peptide (Hymenoptaecin) in two common European bumblebee species

“…Overall, the selective pressure imposed by pathogens might be very similar or even higher in B. lapidarius , although effective population sizes may considerably vary. Bombus terrestris has been shown to exhibit a larger N e (Wolf et al ., ), which might partly be a result of high levels of worker reproduction (Van Honk et al ., ; Van Doorn & Heringa, ; Duchateau & Velthuis, ; Alaux et al ., ; Lopez‐Vaamonde et al ., ), possibly elevating levels of N e compared to B. lapidarius , a species in which worker reproduction is the exception rather than the rule (Free, Weinberg & Whiten, ). Theoretical modelling has shown that worker reproduction in social insects will lead to a decrease in N e in most cases, except under conditions of a strong male‐biased sex ratio (Owen & Owen, ; Nomura & Takahashi, ).…”